Metal recovery and refining furnace



June 23, 1942 R, JANES 2,287,038

I METAL RECOVERY AND REFINING FURNACE Filed Oct. 11, 1959 I INVENTOR. T601 71 26 1?. Jane- Patented June 1942 UNITED STATES I PATENT OFFICE2,287,038

METAL nncovsar m Bummer-macs Thomas R. James, Ianghorne, Pa asignor toSuperior Zinc Corporation, Bristol. h a corporation of PennsylvaniaApplication'bctobel' 11, 1939, Serial No. 299,007

Claims. (01. 266-24) -The present invention relates to smelting andrefining furnaces for metals and ores thereof, and it relates moreparticularly to smelting and refining furnaces for metalswhich may berecovered or refined by vaporization or distillation; and it relatesmore particularly to a furnace for recovering and refining-zinc andother metals having relatively low boiling points.

One of the objects of the present invention is to improve the smelting'of zinc ores, as well as the recovery and purification of zinc fromsecloys and other zinc-bearing or zinciferrous materials;

A further object of the present invention is to permit a greater andmore ready separation of p the several metals which may be present, thatis, to permit the greater and more ready elimination of cadmium and leadfromthe zinc, thereby to recover and -purify zinc more nearly free ofcadmium, lead and other metals. Y

A further object of the present invention is generally to increase theefllciency of the smelting, recovery and refining of zinc and othermetals.

- One. of the common and most widely used methods of smeltingzinciferrous material is to use multiple retort furnaces in which suchmaterial is then heated.

Such furnaces are operated by skilled workmen and produce satisfactoryresults but are expensive to construct and maintain. Labor is arduousand zinc products. Furthermore, control of temperatureis essential foreflicient smelting.

I have invented certain newand useful improvements whereby it ispossibleto construct a large retort through use of sectional structuralmaterials, and certain principles and features of construction. Such alarge retort is an improvement over a multiple retort furnace in manyrespects.

ondary sources such as zinc skimmings, zinc al- It eliminates much ofthe labor of changing. It makes possible much better control oftemperature. It also permits sending a large volume of zinc vapor intoone condenser where improved control over temperature results in higherrecovery of zinc vapor as metal and higher over-all efliciency ofoperation than that of multiple retort furnaces. l

' For the purpose of illustrating -the invention, there is shown in theaccompa ying drawing a form thereof which is at present preferred, sinceit has been found in practice to give satisfactory results, although itis to he understood that the various instrumentalities of which theinvention losses are heavy. Each retort is a separate unit,

delivering but a small amount of vapor and condensation is not uniformbecause of the dimculty of regulating numerous condensers. Also heatingcannot be uniform and hence both efliciency and recovery usually sufler.

Various attempts have been made to enlarge the size of retorts but thesehave been unsuccessful due to limitations of refractories.

In smelting zinciferrous materials, it is necessary to heat thezinc-bearing material with reducing material which causes reduction ofthe zinc to metallic vapor. This also produces an equivalent amount ofvcarbon monoxide and some I carbon dioxide. Carbon dioxide is undesirablesince it tends to reoxidize-some of the zinc vapor and interferes withcondensation of the vapor in metallic state. Prevention of formation ofcarbon dioxide in the smelting zone and in the condensation zone is themost helpful step towards eflicient, operation of a smelting unit. Arelaconsists can be variously arranged and organized and that theinvention is not limited to the precise arrangement and organization ofthe instrumentalities as herein shown and described.

Referring to the drawing in which like reference characters indicatelike parts,

Figure 1 represents a transverse, vertical, crosssectional view,generally on line |l of Figure 2, of a fin-nace em odying the presentinvention, shown more or less schematically, with the elimi-. nation ofthose details of construction which are merely conventional meansgenerally known and used in the art. 1

Figure 2 represents a longitudinally, vertical cross-sectional view,generally on line 2-2 of Figure 1. I

Figure 3 represents a horizontal cross-sectional view, generally on line3-3 of Figure 2.

Figure 4 represents a fragmentary perspective view of the lower smeltingsurface of the furnace embodying the present invention.

The smelting furnace of the present invention includes a bottomdesignated generally by the numeral 5, side walls 8 and I, end walls 8and 9, which together form ashallow receptacle-like chamber havingsubstantial horizontal dimensions, which is covered by an upper heatingroof In which together with the bottom and sides and end walls forms agenerally closed and substantially gas-tight smelting chamber ll havingonly one or inorecharging openings such as the end 7 harging opening I iand the side charging trough tively gas-tight retort is essential forsmelting I: havinga discharge openi g II at the other end thereofoftheheatingtubefl.

through which the metallic vapors are discharged shown).

Above the heating roof 8a, a combustion chamber I4 is disposed havingside walls II and I, end walls I1 and II and anarched heat-reflectorroof I! for reflecting the heat or concentrating the heat onto theheating roof la which also constitutes the .bottom of the combustionchamber l4.

One or more inlet openings are preferably I provided in one of the endwalls (or in one of the side walls) of the combustion chamber l4,through which the fuel and air may be injected under pressure or sprayedinto the combustion chamber, as for instance, by any suitable oil burneror other fuel burner or injector A stack 2| through the roof I! at theopposite end of the combustion chamber It serves to conduct or carryaway the products of combustion.

. In the bottom 5 of the furnace, a series of heating tubes 23 areprovidedfof suitable refractory material such as silicon carbide orgraphite or other refractory ceramic materials, said heatin tubes II.extending horizontally across and ber ll, but of smaller size orcapacity eommensuinto condensers (not beencased in a sheet metal outersheathing it to give support to the furnace and also to make it morenearly gas-tight. The entire furnace may further be supported onpairs-of channel irons 31, to the outer ends of which vertical buckstays38 are secured as at 8!, to give lateral support to the furnace,particularly the lateral walls including the walls I! and I. thereof andthe fire brick arch l8 ;-these buckstays being in turn fastened attheirupper ends by adjustable stay rods or tie rods 40 provided withsuitable turnbuckles ll for adjusting the tension.

Between the blocks 2| and in the juncture of all refractory bricks andslabs constituting the chamber ll, high temperature cement is providedfor filling and sealing the joints or iunctures.

Adrain tap 42 may also beprovided for drawing out all the molten metalwhen it is desired to shut down the furnace. 1

The molten'metal may be fed in through the charging trough l2 from timeto time, or more or less continuously, so as to maintain the level ofthe molten metal to a suitable point which is generally below thelowermost point of the discharge pipe if. The metal is melted in anysuitable melting pot preferably at a point somewhat higher than thecharging trough l2 so as to permit the molten metal to be charged intoand through the trough n by gravity.

In the operation of the furnace, the furnace is first heated to asuitable temperature bycomrate with the-size of the combustion chamberconstituted by the interior of the heating tube.

The heating tubes 23 are preferably arranged with their uppermostportions more or less flush with the horizontal bottom surfaces 2! ofthe smelting chamber ll, soastomore directly transmit the heat into themolten mass of metal insald chamber when it is desired to apply the heatthrough the tubes 23.

The bottom 6 of the furnace is preferably formed of a series ofstaggered refractory-like blocks 20 of suitable size having inwardlyenlarged recesses II in the upper portions thereof asindicatedinl'lgure4,thelocationofsaidrecesses being off center so that by staggerlngtheultimate blocks the can be bro ht into alignment in a manner generallyindicated in Flgures3and4. Thedistanceacrosstheopen-g ing or mouth ofthe greater'than the outer diameter'of the tube 22, so that the tube canbe therein is then filled with'suitahle refractory cement or aggregateII whichisthenpermittedtosetor hardeminsitmsoasflrmlytosetthetnbellin,The heating roof iaisformedofilatslabefl of suitable refractorymaterial such I8 carborundum or ceramic refractories-the adjoiningedgesbeingtongued andgrooved'as atll toform a gas-tight juncture; Eachslab is provided with a reinforcing rib 2|.

Beneath the bottom formed or the blocks a. a

brick or refractory bricks recess is preferably sli ly clearance betweenthe tube 23am! the recess ll bustion of fuel in the combustion ifdesired; also by the combustion chamber I4 and, fuel in the heatingtubes28. Thereafter, the molten metal is fed in through the trough l2'at asuitable level and the molten metal heated gradually to vaporize theseveral component parts thereof.

If desired, cold metal and solid metal pieces or zinc bearing solidmasses may be initially fed into the chamber Ill through'thechargingopening ll either while the furnace is comparatively cold or after ithas been initial charge for heated thereby constituting an the furnace.Thereafter, the

opening H is' preferably closed up with a firebrick or other suitableclosure and after the initial charge of solid material has been molten.the

level of the molten metal can be maintained by charging further moltenmetal into the fir ulh i2. By applying or withholding heat at the bottom(that is. through the heating tubes"), the fractional distillation ofthe component parts of sine bearing materials may be more efficientlyeffected. Thus, by applying bottom heat of sumcient ex tent, therewillbe an ebullition in the mass of. molten metal with the result thatthe cadmium content of the molten metal will be vaporized more quicklyand will be driven on from the molten metal as'v a vapor ingreaterproportion than what would be the case if the heat were merely appliedfrom heat of sufhcient magnitude at the bottom (while also heating fromthe top) the first vaporswhich come of! are more concentrated in cadmiumvafurther base SI maybe formed of suitable fire The lower portion ofthefurnace including the chamber it or the entirefurniwc if desired, may

por.

Thereafter, the bottom heat is shut off or considerably reduced and themolten mass heated;

entirely from above through the heating roof to. Further vaporization ofthe molten mass takes place and the vapor thus driven'oif will containless cadmium than the initial vapor first above described. and by soheating only from above, the zinc isthen vaporized therebyleavingbehindthe lead content of the initial'molten mass. In this manner, thelead may be concentrated in the the top. Thus. by applyin tric heatingunits disposed ready temperature control.

.plying and withholding heat I the tubes maintained having somewhatgreater heating molten mass. As the concentration of the lead graduallyincreases, its solubility in the zinc increases or passes the point ofmaximum solubility of the'lead in the zinc, so that the lead willfurther be concentrated at the bottom. If desired, the molten metalcontaining the higher lead concentration may be drawn off from thefurnace periodically throughthe trough block 42 and then the operationis continued by the further addition of molten zinc bearing metalsthrough the charging trough 12 or by the addition of solid zinc bearingmetals through the charging opening ll.

Vapors discharged through the outlet tube l3 are conveyed to condenserswhere. the vapors are condensed to metallic zinc;with the firstcondensates more rich in cadmium as vhereinabove indicated.

By the foregoing means, the vapors drawn off after the initial removalof cadmium as hereinabove indicatedwill be substantially pure zinc freeof cadmium or other impurities.

By this means, zinc ores and zinc skimmings greater heat conductingcapacity.

.It will also be seen that in the furnace hereinabove described both airand products of combustion are excluded from contact or com-' minglingwith either the molten mass of metal or the metal vapors. The presentinvention may be embodied in other specific forms without departing fromthe spirit or essential attributes thereof, and it is therefore desiredthat the present embodiment be considered in all respects asillustrative and not restrictive, reference being had may be, smeltedand refined efliciently to produce I a substantial pure metallic zinc.

Instead of burning fuel such as oil, gas or powder coal in th heatingtubes 23, electrical heating units may be disposed .within the heatingtubes, such as electric glow bars. Likewise, the upper heat may beobtained by similar elecdirectly beneath the roof 9a of the chamber III,which may be used entirely to replace the upper heating chamber similarto that shown in the bottom or theycan' replace the roof in entirely.

When using electrical heat instead of heat of combustion, the flue orstacks can be eliminated. Thus, if electric heat is used in the heatingtubes 23, the-manifold 24 and pipe 25 are eliminated and the tubes 23are plugged at both ends by refractory, so as to retain the heat andindeed are shortened so as not to extend substantially beyond the widthof the metal-vaporizing chamber 'II, (the electrical conductorsextending through 21.1? furnace wall to the opposite ends of the tubesIt is to be understood that the zinc vapor discharged through thedischarge ll may also be converted into zinc oxide and'any other zincproducts which can made from zinc vapor.

By imbedding the heating tubes 23 in the manner indicated particularlyin Figures 2, 3 and 4, the tendency of the tubes to float in the com:

' vparatively heavier molten metal is overcome andfirmlyin place. r

The blocks 29 are preferably of a fire clay tile going description tothe appended claims rather than to .the forevention.

Having thus described the invention, what is hereby claimed as new anddesired to be secured by Letters Patent is 1. A metal-vaporizing furnaceincluding a plurality of heating tubes embedded in the bottom of saidmetal-vaporizing chamber, with small uppermost parts of the walls ofsaid tubes-constituting a portion of the bottom of said metalvaporizingchamber.

2. A, furnace including a material-processing chamber formed ofrefractory materialsof relatively low heat conductivity and heatingtubes in the bottom of said chamber formed of refractories of relativelyhigher conductivity, with small uppermost parts of said tubesconstituting portions of the bottom of said chamber.

3. A metal-vaporizing furnace comprising a substantially rectangularmetal-vaporizing chamber, means for applying indirect heat from above, aplurality of transverse heating tubes disposed beneath said chamber andhaving small uppermost portions thereofv constituting portions of thebottom of said chamber, and means for independently controlling thesupplyof fuel to each of said tubes whereby the several tubes may beused, independently of eachother and independently of the upper heatingmeans, for applying indirect heat to said chamber from below.

4. In a metal-vaporizing furnace, means for accurately applying indirectheat tothe chamber containing the molten material, said heating meanscomprising a plurality of" tubes partially embedded in the floor of saidchamber and having'small uppermost portions thereof forming part of thebottom of said chamber; each of said tubes being provided with aseparate and individually-controllable fuel-injector whereby the severaltubes may be used independently of each other for transmitting heat tothe molten material.

5. A metal-vaporizing furnace comprising a rectangular shallowmetal-vaporizing chamber, a

- fiat heating roof above said chamber and forming the upper wallthereof, said heating roof being formed of adjacent refractory slabsextendin: across the smaller horizontal dimension of said furnace withtheir opposite ends supported only by the longitudinal walls of saidmetal-' vaporizing chamber, the juncture between adja having relativelypoor or relatively low-heat con ducting capacity, while the tubes 23 areprefer. ably silicon carbide or, carborundum or graphite conductingcapacity so as to promote the flow of the heat from the tubes upwardlyinto the bath of molten metal. 50, too, the cement or aggregatefilling-ll may cent refractory slabs being generally sealed againstpassage of vapor therethrough, means for.

applying heat to the top of said chamber, and a plurality of heatingtubes partially embedded in the bottom of-said metal-vaporizing chamberwith small'uppermost'parts of said tubes constituting a portion of thebottom of said metal vaporizing chamber.

6. A metal-vaporizing furnace comprising a rectangular shallowmetal-vaporizing chamber,

a flat heating roof above said chamber and contain carborundum or otherrefractcry havingto indicate the scope of the informing the upper wallthereof, said heating roof being formed of adjacent refractory slabsextending across the smaller horizontal dimen sion of said furnace withtheir opposite ends supported only by the longitudinal walls of said 5metal-vaporizing chamber, the juncture between adjacent refractory slabsbeing generally sealed against passage of vapor therethrough, means forapplying heat 'to the top of said chamber, and a plurality of heatingtubes partially embedded in the bottom of said metal-vaporizing chamberwith small uppermost parts of said tubes constituting a portionof thebottom of said metalvaporizing chamber; each of said heating tubes beingprovided with an individual fuel-injector whereby the several tubes maybe used; independently of each other and independently of the upperheating means, for applying indirect heat to said chamber from below.

l '7. Ametal-vaporizing furnace including .an

oblong shallow metal-vaporizing chamber having a substantially uniformvertical dimension throughout, a hat heating roof above said chamber andforming the upper wall thereof, said heating roof being formed ofadjacent refractory slabs extending across the smaller horizontaldimension of said chamber, with their opposite ends supported by thelongitudinal walls of said chamber, a flat heating floor forming thebottom of said chamber, a plurality of heating tubes embedded in saidfloor, means for applying heat to the top ofsaid chamber, and means forheating said tubes independently of each other; said last-mentionedheating means including a .separate fuel-injector operatively connectedwith 5 each of said tubes.

8. A metal-vaporizing furnace including an oblong shallowmetal-vaporizing chamber havin a substantially uniform verticaldimension throughout, aflat heating roof above said chami ber andforming the upper wall thereof, said heating roof being formed ofadjacent refractory slabs extending across the smaller horizontaldimension of said chamber, with their oppoacross the smaller horizontaldimension of said i chambe means-for heating said chamber from above,and means for applying heat individually to each of said heating tubeswhereby said heating tubes can be used independently of each other forheating said chamber.

' 9. A metal-vaporizing furnace includlnsan oblong shallowmetal-vaporizing chamber having a substantially uniform verticaldimension throughout, a flat heating roof above said chamber and formingthe upper wall thereof, said heating roof being formed of adjacentrefractory slabs extending acres the smaller horizontal dimension ofsaid chamber, with their opposite ends supported by the longitudinalwalls of said chamber, aflat heating floor forming the bottom of .saidchamber, .a plurality of heating tubes embedded in said floor, means forapplying indirect heat to said chamber from above, and a separate andindividually-controllable fuel burner operatively connected with each ofsaid heating tubes.

10. A metal-varopizing furnace including an oblong shallowmetal-vaporizing chamber having a substantially uniform verticaldimension throughout, a flat heating roof above said chamber and formingthe upper wall thereof, said heating roof being formed of adjacentrefractory slabs extending across the smaller horizontal dimension of'said chamber, with their opposite ends supported by the longitudinalwalls of said chamber, said slabs having'reinforcing ribs extendinglongitudinally thereof and integral i therewith, the juncture betweenadjacent reiractory slabs being sealed against passage of vaportherethrous a flat heating floor formingthe bottom of said-chambe aplurality of heating tubes embedded in said floor, means for applyingheat to the top of said chamber, and means for heating said tubesindependently of, each other; said last-mentioned heating meansincluding a separate fuel-injector operatively consite ends supported bythe longitudinal walls of 45, .said chamber, a flat heating floorforming the nected with each of said tubes. I THOMAS R. JANES.

